Season long availability of nutrients, especially nitrogen (N), is essential in corn production. To ensure adequate supplies of N are available to the crop, producers can utilize several N deficiency monitoring methods. By monitoring N status, farmers can more effectively manage additional nitrogen applications, saving time and money.Crop Scouting1

Actively scouting a corn crop enables farmers to notice nutrient deficiencies when symptoms first appear. For nitrogen deficiencies, look for v-shaped yellowing beginning at the leaf tip and progressing along the midrib. Symptoms appear on lower leaves first and work their way up the corn plant. Other symptoms include spindly stalks, stunted growth and small ears.

Pre-sidedress Soil Nitrate Test1

The pre-sidedress soil nitrate test (PSNT) determines the amount of nitrate-N available in the soil, which can be used to decide if enough N is available to meet crop requirements. Producers collect soil samples just prior to sidedressing, the time corn begins rapid N uptake. The PSNT is best suited for fields with high N mineralization potential, such as fields high in organic matter, fields previously in legumes or fields where manure is applied. One item to note, farmers should not apply preplant N fertilizer to fields when using PSNT to monitor N levels.

Leaf Tissue Analysis2

A leaf tissue analysis reveals the nutrient levels in plants when the sample is collected. Based on the analysis, farmers can evaluate whether or not nutrient supplies are adequate to meet crop needs. Samples can be taken throughout the season, however waiting until later in the growing season, closer to tasseling, provides a better indication of possible N deficiency.

Chlorophyll Meters1

A chlorophyll meter measures the amount of N a plant has by estimating the chlorophyll content or greenness in the corn leaf. Producers collect an average reading from 20 to 30 plants. Then, the average is compared to the average reading from an N-reference strip, an area in the field where higher amounts of N is applied and is considered to have non-limiting supplies of N.

This allows growers to determine the amount of additional N to apply. For the chlorophyll meter test, corn must have reached the V6 stage, yet, it is suggested to wait until later vegetative stages to determine fertilizer needs. By waiting growers have a more accurate reference for additional N rates, however, waiting requires using high clearance equipment to apply fertilizer.